Issue 6, 2022

Identification of non-traditional coordination environments for iron ions in nickel hydroxide lattices

Abstract

The uniformity in electrochemical behavior of FexNi1−x(OH)2 is remarkable given the diversity in published fabrication protocols, composition-dependent structural changes, and multitude of electrochemical reaction mechanisms proposed. We use complementary techniques to show that multiple unique Fe(III) coordination environments exist in FexNi1−x(OH)2 synthesized by alkaline precipitation. Samples synthesized with formamide added to the reaction vessel yield Mössbauer and Raman spectra consistent with Fe(III) successfully incorporated into the Ni(OH)2 lattice. Additional spectroscopic features emerge for samples synthesized in the absence of formamide, revealing a second Fe(III) coordination environment. Correlations in structural information derived from the numerous characterization techniques suggest that the secondary environment sits atop the 2-dimensional Ni(OH)2 sheets. X-ray diffraction and X-ray absorption spectroscopy fail to resolve this second site, but show that Fe(III) induces a non-uniform structural contraction that distorts the Ni(OH)2 lattice for all samples. Electrocatalytic oxygen evolution is qualitatively similar for both sample series, but samples synthesized in the presence of formamide consistently outperform those from conventional pH precipitation. Iron ions within the Ni(OH)2 lattice are therefore deemed to be the catalytically relevant structural feature. The identification of a secondary iron site demonstrates that qualitative similarities in electrochemical behavior mask quantitative differences in structure and electrocatalytic competence.

Graphical abstract: Identification of non-traditional coordination environments for iron ions in nickel hydroxide lattices

Supplementary files

Article information

Article type
Paper
Submitted
03 פבר 2022
Accepted
16 מאי 2022
First published
16 מאי 2022

Energy Environ. Sci., 2022,15, 2638-2652

Identification of non-traditional coordination environments for iron ions in nickel hydroxide lattices

E. P. Alsaç, K. Zhou, W. Rong, S. Salamon, J. Landers, H. Wende and R. D. L. Smith, Energy Environ. Sci., 2022, 15, 2638 DOI: 10.1039/D2EE00396A

To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page.

If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given.

If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page.

Read more about how to correctly acknowledge RSC content.

Social activity

Spotlight

Advertisements